This invention is related to the art of kinetic spectroscopy wherein gases either desorbed from or resulting from a catalytic reaction on a substrate surface are detected as a function of the temperature of the surface, generally referred to as temperature programmed desorption spectroscopy.
The art of thermal desorption spectroscopy is primarily directed to the study of substrate surfaces by analyzing the characteristics of desorption of controlled gaseous molecules from the surface. When a solid surface is exposed to gaseous molecular species, the species often form an adsorbed layer on the solid surface. The molecules adhere to the surface by either chemical or physical bonds. The high area substrate material is often in the form of small particles which are held in a bed of particles. The temperature of this bed is gradually increased in a vacuum or carrier gas environment. Gases desorbed from the surface area of these particles are analyzed by instruments such as a gas chromatograph or a mass spectrometer. The desired information output is the change in partial pressure in the desorbed gas as a function of the temperature of the bed of substrate particles. Peaks in differential partial pressure occur at different bed temperatures, providing information on the characteristics, including composition, of the substrate particle surface as it interacts with the adsorbed species under investigation.
There are certain recognized limitations of this technique. One such limitation is that diffusion through the bed of particles may interfere with measurements of desorption rates. That is, gas molecules desorbed from one particle may be adsorbed by another and then again desorbed before escaping the bed of particles and reaching the gas analyzer. Another difficulty is maintaining the temperature of all particles in the bed at the same temperature as the temperature is programmed upwards. The undesired result of these two factors is that the output data is blurred; that is, the desired sharp peaks of differential partial pressure do not appear but rather are blurred together.
The approach taken by existing technology is to extract the desired peak information from the blurred output data. This involves complicated computer implemented processing of that data. It is a principal object of the present invention to provide a technique for measuring the desired desorption peaks in a simpler and more accurate way.
It is a further object of the present invention to provide a system and general technique for all types of temperature programmed spectroscopy, including, in addition, the investigation of catalytic reaction chemistry, pore diffusion in porous substrate materials, and catalyst preparation using hydrogen or other gaseous reducing agents.